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A late-stage assembly checkpoint of the human mitochondrial ribosome large subunit

Pedro Rebelo-Guiomar1, Simone Pellegrino2,3,4, Kyle C Dent2,3,4,5

  • 1MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Rd, Cambridge, CB2 0XY, UK.

Nature Communications
|February 18, 2022
PubMed

Insights

Mitochondrial ribosome biogenesis relies on 2'-O-methylation of 16S mt-rRNA by MRM proteins. MRM2 is crucial for mitochondrial respiration and mitoribosome assembly, independent of its methyltransferase activity.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • Post-transcriptional RNA modifications regulate cellular processes like ribosome biogenesis.
  • Human mitochondrial ribosomes (mitoribosomes) are essential for energy production.

Purpose of the Study:

  • To investigate the role of 2 -O-methylation in human mitochondrial ribosome biogenesis.
  • To elucidate the function of MRM proteins in mitoribosome assembly and mitochondrial homeostasis.

Main Methods:

  • Genome-wide analysis of the human mitochondrial transcriptome.
  • Cryo-electron microscopy (cryo-EM) to visualize mitoribosomal large subunit (mtLSU) particles.
  • Analysis of MRM2 orthologue in Drosophila melanogaster.

Main Results:

  • 2 -O-methylation is confined to 16S mt-rRNA in the human mtLSU, catalyzed by MRM1, MRM2, and MRM3.
  • MRM2 is critical for mitochondrial respiration and mtLSU assembly, with its methyltransferase activity being non-essential.
  • Absence of MRM2 leads to disordered mtLSU particles and affects assembly intermediates.
  • Disruption of the MRM2 orthologue in Drosophila causes developmental arrest.

Conclusions:

  • MRM2 plays a vital, non-enzymatic role in mtLSU assembly, acting as a checkpoint for mitochondrial homeostasis.
  • This study reveals a key regulatory mechanism in mitoribosome biogenesis essential for mitochondrial function.

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